Interlocking control system



April 3, 1962 o. G. LEWIS INTERLOCKING CONTROL SYSTEM Filed July 8, 1960Oliver 6. Lewis Inventor Potent Aflorney United States Patent 3,027,723ENTERLDCKiNG CONTROL SYSTEM Oliver G. Lewis, Westfield, NJ., assignor toEsso Research and Engineering Company, a corporation of Delaware FiledJuly 8, 1960, Ser. No. 41,646 2 Claims. (Cl. 60-97) The presentinvention relates to an interlocking control system and moreparticularly to an apparatus for interlocking a plurality of operationsto insure proper operating sequence. The invention has variousapplications and in general can be used in connection with a pluralityof reciprocating or oscillating elements, particularly where it isdesirable to prevent one operation occurring until after a relatedoperation has been completed or has passed a critical phase. A moreparticular application of the present invention is related to apparatusof a general type which is used in carrying out a sequence of operationsfor testing or analytical purposes; for example, an apparatus which isdesigned to take a series of samples of lubricating oil, measure theirviscosity, record the measurements and reuse the testing equipment, withappropriate washing or cleaning between operations, to repeat this typeof test any desired number of times.

In one apparatus of this type, a container of the oil to be sampled isbrought to a certain point in a conveyor system, is then lifted to asampling position where a sample of oil is withdrawn therefrom by asampling unit and tested, and after the test is completed the samplemoves on down the line to a place where the analysis is recorded on thesample container. Such a system operates to prevent mis-application ofdata since it insures that each sample has recorded thereon its properreading. Thereafter the sampling unit is drained into a receiver whichis moved into the position just vacated by the container, the timingbeing such as to prevent interference but also to prevent spillage ofthe oil.

In a preferred type of operation, the various sequential operations areperformed by fluid pressure, i.e., by hydraulically or pneumaticallyoperated pistons with suitable control elements which may be eithermechanical valves or electrical controls. The particular nature of theinvention will be better understood by referring to the accompanyingdrawing in which:

FIG. 1 is a fragmentary view in elevation of an automatic viscometersystem involving fluid pressure or hydraulically operated pistons withan interlocking control system according to the present invention;

FIG. 2 shows a preferred form of interlocking control for the assembliesof the system in FIG. 1;

FIG. 3 shows an alternative interlocking control systern; and

FIG. 4 shows an electrically operated interlocking control system whichcan be used in place of those previously illustrated.

Referring first to FIG. 1, for background the general apparatus willfirst be described. A conveyor, not shown, brings an open vwsel Vcontaining oil or other material to be sampled to a position above aplatform 11 which is operated through fluid pressure by a piston incylinder 13 connected by piston rod 15 to the member '11. Suitablepressure fluid, e.g., hydraulic, is supplied through line 17 so that atthe proper instant the platform 11 is raised to bring the vessel up to apoint where it encloses the sampling nozzle 19. The latter is connectedto means, not shown, for drawing a sample of the liquid upwardly,passing it through a viscosity testing operation, and thereafterreturning the bulk of the sample to the vessel. The raised position ofthe platform is indicated in dotted lines at 11A.

After the oil in nozzle 19 has been returned to the "ice containerexcept for a small dripping residue, platform 11 is lowered to itsoriginal or extreme bottom position. Thereafter a drain pan 21 isshifted about a vertical axis, moving to the left in FIG. 1, by pistonrod 23 which is disposed to bear upon but is not fixedly connected tothe drain pan. This piston rod is actuated by a piston in the fluidpressure cylinder 25. The latter is supplied by suitable operating fiuidwhich may be hydraulic, for example, through line 27. This drain pan 21catches the drainings from tube 19. The height of the drain pan 21 isdetermined by a piston in cylinder 31 connected by piston rod 33 to thepan 21 which can rotate about this support. Thus the pan 21 may beraised and lowered as well as moved into or out of position beneathsampling device 19. Admin 35 connected to a suitable disposal point bymeans of a tube, not shown, takes care: of the drainings. The containeris then taken on to another station, not shown.

The piston rod 33 is operated by suitable means, e.g., hydraulic fluidsupplied through line 37 as will be obvious.

Means for supplying actuating fluid under pressure are indicated in theform of a pump of any suitable type at 41, primary control being throughsolenoid operated valves 43, 45 and 47 in lines 17, 27 and 37respectively. These valves, however, may not close completely or onexact time schedule; moreover, there is frequently a certain amount ofresilience or bounce in the pressure system so that closely timedsequences are hard to achieve. However, certain safety features arerequired.

From the foregoing it will be clear that there must be not only propersequential operation, but also positive prevention of untimely operationof the pistons or piston rods such as 15, 23 and 33.

Referring now to FIG. 2, there is shown a fluid pressure cylinder 51having therein a movable piston 53 which operates a piston rod 55. This.cylinder 51 may correspond with cylinder 13 and may, if desired, beidentical therewith so that piston rod 55 of FIG. 2 is in fact anextension 55A of the piston rod 15 in FIG. 1. A suitable hydraulic orpneumatic motor unit indicated at 57 may be the operator for a controlvalve such as valve 45 in line 27 of FIG. 1. This unit 57 in one formcorresponds to hydraulic cylinder 25 and its piston, FIG. 1. The rod 55of FIG. 2 is provided with a cross-head member 61 which at theappropriate moments contacts a plurality of control plungers 63, 71.Plunger 63 controls a block valve 65 which is connected through line 66to the valve or operating motor 57. In practice, valve 65 preferablywould be inserted in line 27 between electrically controlled valve 45and hydraulic cylinder 25, FIG. 1. This is indicated diagrammatically at650, FIG. 1. Now if pressure of pump 41 should inadvertently be appliedto line 27 (and line 77, (FIG. 2, which connects therewith), beforepiston rod 15 (and the vessel V) have reached extreme low position,valve 65 will positively block pressure to cylinder 57 and preventmovement of piston 67. The unit comprising cylinder 57 and piston 67 hasa reciprocal operating rod 69 which may be connected through means notshown to initiate opening of control valve 45 to cause the nextsequential operation in the principal apparatus. At the approximate timethe cross-head 61 will contact the other control plunger 71 in thesecond valve element 73 to permit the operating fluid to flow out ofcylinder 57 through line 75 at the proper time, but prevents outflow offluid from the cylinder prior to such proper time and cooperates withvalve 65 to prevent movement of piston 67 in either direction except atthe precise time desired. In these operating controls, the operatingfluid is brought in through line 77 and passes out through line 79 inthe sequence just described.

When the cross-head 61 moves away to the right, the

plungers 63 and 71 are moved also to the right by springs, not shown, toclose valves 65 and 73 and this locks the piston 67 in a fixed position.Thus, valves 65 and 73 may be used as locks to prevent any possiblemisoperation of piston 67 unless and until the rod 55 has reached itsproper position. The arrangement of cylinder 13 in vertical position inFIG. 1 and of cylinder 51 in horizontal position in FIG. 2 is of courseoptional.

A similar arrangement is shown in FIG. 3, except that the valves 65A and73A have plungers 63A and 71A operated by rocker arms 81 and 83respectively. Each of these arms has a pivotal mount 85 on valve 65A, or87 on valve 73A, and each has a cam following roller 89 on its oppositeend. A cross-head member 91 has suitable cam-like surfaces on its upperand lower ends which serve to operate the rollers 89 and actuate thevalves in obvious manner.

Valve 65A connects through line 95 to line 97 of the master controlvalve operating motor 99. The latter contains a piston 101which operatesa control rod 103 and the latter is connected to a suitable valve suchas 45 or 47 to control operation in the proper time sequence. The unit99, 101 may of course replace the motor unit 25, or unit 31 of FIG. 1 ifdesired.

Referring now to FIG. 4, there is shown an electrical system combinedwith a pneumatic or hydraulic cylinder and piston for accomplishingdesired sequential controls for similar purposes. Here a cylinder 111 isprovided with movable piston 113 which operates piston rod 115. Thelatter has mounted thereon a plate or disc member 117 which may beadjustably positioned along the rod 115 by suitable fastening means suchas a set screw 119. The plate or disc 117 carries a plurality of arms ofdifferent length indicated at 121, 123 and 125 respectively. Each ofthese carries a small active magnet M1, M2 or M3.

Mounted on the cylinder 111 in such position as to be operated by therespective magnets are a plurality of magnetically operable reedswitches of known commercial type. These are spark-proof, being enclosedin glass or other suitable tubing to avoid fire or explosion hazards inthe presence of highly combustible materials. Switch S1 is in positionto be operated by magnet M1 as the piston 113 moves to the extreme rightand the plate or disc 117 is in its farthest position from the cylinder111. This switch S1 is connected by electrical leads L1 to a firstcontrol circuit not shown, but for example, may be the circuit whichoperates solenoid valve 43 in FIG. 1. Subsequently as the piston 113moves to the left, magnet M2 approaches switch S2 and activates a secondcircuit which may, for example, be connected to solenoid operated valve45 of FIG. 1 through leads L2. Finally, the switch S3 is approached bymagnet M3 when piston rod 115 is fully retracted, and at the properinstant this operates the reed switch to activate a circuit throughleads L3 to initiate a third operation, for example, the operation ofsolenoid valve 47 of FIG. 1.

Obviously by varying the lengths of the bars 121, 123 and 125 or thepositioning of switches S1, S2 and S3, any desired time sequence may beobtained. The plate or disc 117 may be mounted on one of the operatingpiston rods of the system such as rod 55A of FIG. 1 as will be obviousto those skilled in the art.

It is realized of course that numerous interlocking control systems havebeen devised for many purposes in the past, but the system abovedescribed is completely safe, is very simple, and makes use of necessaryoperating elements of the system to be controlled so that it requires abare minimum of additional elements to place effective interlockingcontrols over the whole sequence of operations. All the operations maybe performed by hydraulic pressure fluid, or by pneumatic fluid, or by acombination of the two. Electrical solenoid operations, suitablydampened by fluid control means or equivalent may be substituted whereappropriate.

It Will also be understood that while the invention has been describedin connection with a particular use or application, it also has otheruses and applications of various types which will suggest themselves tothose skilled in the art. It is therefore intended to cover theapplication broadly of this control system, as far as permissible by theprior art and the scope of the following claims.

What is claimed is:

1. In a system containing a plurality of cyclically operable fluidpressure operated pistons for performing separate operations in adesired sequence and a fluid pressure line for supplying operatinghydraulic fluid to each of said pistons, the improvement which consistsin (1) first actuating means moved by a first one of said pistons, (2)first control means in the path of said first actuating means to beactuated thereby in proper timed relation to the travel of said firstpiston, said first control means including an electric switch and magnetoperating means therefor which are moved relatively to each other bymovement of said first piston to cause said first control means tofunction at the desired time and in the desired sequence, and said firstcontrol means being connected in said fluid pressure line for positivelypreventing movement of at least a second piston before said first pistonhas reached a predetermined position in its operating cycle, and (3)second control means for operating said second piston when suchpredetermined position of said first piston is reached.

2. The improvement according to claim 1 in which said electric switch isa glass-enclosed reed switch, and said magnet operating means thereforis disposed to be moved back and forth with respect thereto in line withmotion of said first piston.

References Cited in the file of this patent UNITED STATES PATENTS

